1. Field of the Invention
The present invention relates generally to a liquid-lens assembly using an electrowetting phenomenon and, more particularly, to a liquid-lens assembly, in which the structure for applying current to a liquid-lens module is simplified.
2. Description of the Related Art
Currently, a camera having a controllable focus function is applied to various kinds of portable multimedia equipment, including a mobile communication terminal, a small digital camera, an automatic camera, etc. As technology is gradually developed, efforts to integrate various devices, including a camera, into a single piece of mobile equipment and miniaturize the equipment have been continuously conducted.
In the case of a conventional camera having the controllable focus function, a conventional lens having the controllable focus function is constructed to move along the optical axis of the lens because physical movement of the lens is required in order to set the focus. Hence, the conventional camera must have a large size to some extent. Further, since additional parts required for driving the lens, such as a motor, must be mounted, it is difficult to realize miniaturization of the camera.
Recently, as a camera equipped with a lens having a controllable focus function has been attached to a portable terminal, miniaturization of the camera is more keenly required. Further, when the controllable focus lens is driven in the mechanical method, as in the prior art, problems other than the above-mentioned problems occur. That is, since an electric motor installed to drive the controllable focus lens consumes a considerable amount of battery power, it is technically difficult to mount the controllable focus lens to a mobile terminal. Moreover, in order to control the focus of the lens using the conventional mechanical method, a certain amount of time is required.
Thus, in order to solve the problems, recently, a liquid lens using an electrowetting method has been proposed as an alternative to a conventional zoom lens operated by the mechanical method. Research on the liquid lens has been actively conducted.
The basic construction and function of the liquid lens will be briefly described with reference to PCT WO 03/069380, which discloses the invention dealing with the liquid lens.
FIG. 1 is a schematic sectional view showing the liquid lens disclosed in PCT WO 03/069380. The liquid lens will be described with reference to the drawing. As shown in FIG. 1, the liquid lens includes a cylindrical fluid chamber 5, a fluid contact layer 10, a first electrode 2, and a second electrode 12. The fluid chamber 5, having a cylindrical wall, holds a first fluid A and a second fluid B which have different refractive indices, are in contact over a meniscus 14, and are non-miscible. The fluid contact layer 10 is arranged on the inside of the cylindrical wall. The first electrode 2 is separated from the first fluid A and the second fluid B by the fluid contact layer 10. The second electrode 12 functions to activate the second fluid B.
In this case, the first electrode 2 has a cylindrical shape, is coated with an insulating layer 8, and is made of a metallic material. The second electrode 12 is positioned on one side of the fluid chamber 5. Further, a transparent front part 4 and a transparent rear part 6 form a cover of the fluid chamber 5, which holds the two fluids therein.
The operation of the liquid lens, constructed as described above, is as follows.
When no voltage is applied between the first and second electrodes 2 and 12, the fluid contact layer 10 has higher wettability by the first fluid A compared to the second fluid B. If voltage V1, V2, or V3 is applied between the first and second electrodes 2 and 12, the wettability relative to the second fluid B varies because of the electrowetting effect, and the contact angle Q1, Q2, or Q3 of the meniscus 14 with the liquid contact layer 10 varies, as shown in the drawings. Thus, the shape of the meniscus 14 varies depending on the applied voltage, and the focus of the liquid lens is controlled using the variation in shape of the meniscus 14.
That is, as shown in FIGS. 1 to 3, the angle between the meniscus 14 and the fluid contact layer 10 measured at the first fluid B according to the magnitude of applied voltage is changed from an obtuse angle to an acute angle, e.g., 140°, 100°, and 60°. In this case, FIG. 1 shows an arrangement having high negative power, FIG. 2 shows an arrangement having low negative power, and FIG. 3 shows an arrangement having positive power. Such a liquid lens using the fluids is advantageous to realize miniaturization of the equipment and reduce power consumption, compared to the conventional lens, the focus of which is controlled in the mechanical driving method.
Meanwhile, as shown in FIGS. 1 to 3, the conventional liquid-lens module is constructed so that an electric wire 15 is directly connected to the liquid-lens module to apply current to the fluid.
However, as described above, according to the conventional method of directly connecting the electric wire to the liquid-lens module, the electric wire must be connected to a connecter which is provided outside the liquid-lens module. Thus, the electric wire must be additionally treated. Further, since the electric wire is provided outside the liquid-lens module, the appearance thereof is untidy. Furthermore, the method of applying current through the electric wire is problematic in that the reliability of the power supply is low.
The basic operational principle and construction of the liquid lens are described with reference to the drawings. The overall construction of a liquid lens assembly, required to apply the liquid-lens module to an end product in practice, and the concrete method of applying current have not been disclosed yet.
Therefore, the applicant of this invention proposes ways to solve the above-mentioned problems.